• Hannu Manninen, Kimmo Mäkinen, Ritva Vanninen, Antti Ronkainen, and Harri Tulla.
• Diagnostic Medical Imaging Centre, Department of Radiology, Kuopio University Hospital and Kuopio University, Puijonlaaksontie 2, 70210, Kuopio, Finland. hannu.manninen@kuh.fi
• Acta Neurochir (Wien). 2009 Sep 1;151(9):1099-105.

PurposeTo evaluate the prevalence of anatomical variations in the circle of Willis predisposing to cerebral ischemia during intraoperative closure of a carotid artery.MaterialsAnatomy of the cerebral arteries of 92 deceased was assessed by angiography and permanent silicone casts. Cerebral ischemia during closure of a carotid artery with patent contralateral internal carotid artery (ICA) was considered possible in cases of simultaneous nonfunctioning anterior communicating artery (diameter <0.5 mm) and ipsilateral posterior communicating artery (PComA) (diameter <0.5 mm or fetal type posterior cerebral artery). In cases of contralateral ICA occlusion, cerebral ischemia was considered possible if ipsilateral PComA was nonfunctioning.ResultsCerebral ischemia during closure of the right or left carotid artery with patent contralateral ICA was estimated to be possible in 16 (17.4%) and 13 (14.1%) cases. In cases of occluded contralateral ICA, the corresponding numbers were 55 (59.8%) and 49 (53.3%). A review of magnetic resonance and catheter angiographies also identified other variants of the circle of Willis with increased risk.ConclusionsIncomplete circle of Willis predisposes approximately one-sixth of individuals to cerebral ischemia during transient closure of carotid artery but the risk is more than threefold in case of contralateral ICA occlusion.

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